codegen: Add assertions to detect missing delegate target values
codegen: Add assertions to detect missing delegate target values

GNOME/vala,severinh/vala,spidermonkdust/vala,xdave/pvala,kamanashisroy/aroop,spidermonkdust/vala,jessevdk/vala,GNOME/vala,rvu95/vala,severinh/vala,kamanashisroy/aroop,flobrosch/vala-fixes,tjol/vala-tjol,severinh/vala,tjol/vala-tjol,jessevdk/vala,frida/vala,playya/vala,Distrotech/vala,flobrosch/vala-fixes,GNOME/vala,Distrotech/vala,frida/vala,Distrotech/vala,kamanashisroy/aroop,playya/vala,playya/vala,flobrosch/vala-fixes,frida/vala,rvu95/vala,spidermonkdust/vala,frida/vala,frida/vala,tjol/vala-tjol,GNOME/vala,rvu95/vala,jessevdk/vala